1. Field of the Invention
This invention relates to a beam rotation angle detecting apparatus used in a rotary encoder, a linear encoder or the like to optically effect position detection, and a rotation detecting apparatus and a beam rotation angle detecting method.
2. Related Background Art
Heretofore, to obtain the rotation angle of a beam rotating while forming a track as a circle, as disclosed in Japanese Patent Application Laid-Open No. 6-235622 and Japanese Patent Application Laid-Open No. 6-347289, the light receiving position thereof has been detected by a circular ring-shaped or circular light receiving sensor for receiving a beam.
Also, U.S. Pat. No. 4,760,436, discloses regarding that two beams are received by independent arcuate light receiving sensors, and these sensors are used properly in conformity with the rotation angle to thereby detect a round of continuous angle.
In the above-described beam rotation angle detecting apparatus, however, there has been the problem that the rotation angle of a beam cannot be accurately detected under the influence of the deviation between the center of rotation of the beam and the center of the light receiving sensor.
It is an object of the present invention to solve such a problem peculiar to the prior art and provide a beam rotation angle detecting apparatus which can accurately detect the rotation angle of a beam, and a rotation detecting apparatus and a beam rotation angle detecting method.
Other objects of the present invention will become apparent from the following description of some embodiments of the invention.